High LET radiation enhances apoptosis in mutated p53 cancer cells through Caspase-9 activation
High LET radiation enhances apoptosis in mutated p53 cancer cells through Caspase-9 activation
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DOI：
10.1111/j.1349-7006.2008.00818.x
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发表时间：
2008-07-01
期刊：
影响因子：
5.7
通讯作者：
Ohnishi, Takeo
中科院分区：
文献类型：
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作者：
Yamakawa, Nobuhiro;Takahashi, Akihisa;Ohnishi, Takeo
尽管p53基因突变可导致对放疗、化疗和热疗的抗性，但高线性能量转移（LET）辐射诱导细胞凋亡，而不管癌细胞中p53基因的状态如何。本研究的目的是阐明高LET辐射诱导细胞凋亡的机制。用X射线、C-离子（13 - 100 KeV/μ m）或Fe-离子束（200 KeV/μ m）照射含有突变的p53（mp53）基因的人牙龈癌细胞（Ca 9 -22细胞）。使用集落形成测定法测定细胞敏感性。Hoechst 33342染色检测细胞凋亡并定量。Western blotting和流式细胞术检测Caspase-3活性。用高LET辐射照射的细胞显示出高敏感性和高频率的凋亡诱导。存活分数和凋亡诱导的相对生物有效性（RBE）值以LET依赖性方式增加。两条RBE曲线在100 KeV/μ m处达到峰值，然后在超过100 KeV/μ m的值处下降。当用高LET辐射照射细胞时，胱天蛋白酶-3被切割和激活，导致聚（ADP-核糖）聚合酶（PARP）切割。此外，Caspase-9抑制剂抑制Caspase-3激活和凋亡诱导高LET辐射在更大程度上比Caspase-8抑制剂。这些结果表明，即使在mp53存在下，高LET辐射也通过激活Caspase-3至Caspase-9来增强细胞凋亡。
Although mutations in the p53 gene can lead to resistance to radiotherapy, chemotherapy and thermotherapy, high linear energy transfer (LET) radiation induces apoptosis regardless of p53 gene status in cancer cells. The aim of this study was to clarify the mechanisms involved in high LET radiation-induced apoptosis. Human gingival cancer cells (Ca9-22 cells) containing a mutated p53 (mp53) gene were irradiated with X-rays, C-ion (13 - 100 KeV/mu m), or Fe-ion beams (200 KeV/mu m). Cellular sensitivities were determined using colony forming assays. Apoptosis was detected and quantified with Hoechst 33342 staining. The activity of Caspase-3 was analyzed with Western blotting and flow cytometry. Cells irradiated with high LET radiation showed a high sensitivity with a high frequency of apoptosis induction. The relative biological effectiveness (RBE) values for the surviving fraction and apoptosis induction increased in a LET-dependent manner. Both RBE curves reached a peak at 100 KeV/mu m, and then decreased at values over 100 KeV/mu m. When cells were irradiated with high LET radiation, Caspase-3 was cleaved and activated, leading to poly (ADP-ribose) polymerase (PARP) cleavage. In addition, Caspase-9 inhibitor suppressed Caspase-3 activation and apoptosis induction resulting from high LET radiation to a greater extent than Caspase-8 inhibitor. These results suggest that high LET radiation enhances apoptosis by activation of Caspase-3 through Caspase-9, even in the presence of mp53.